If you're using a wet fresh ricotta or one that's a bit looser than typical store-bought varieties, you'll need to strain it beforehand. Place the ricotta in a fine-mesh strainer or cheesecloth over a bowl for at few hours prior to assembling.
In a bowl, combine the ricotta, well-strained spinach, Parmesan cheese, semolina flour, egg, and 1–2 generous pinches of kosher salt. Mix with your hands until everything is fully incorporated.
Using a 1 tbsp cookie scoop, portion out 1 tbsp or 2 tbsp ricotta balls and roll them in flour, shaking off the excess and rest them on a sheet tray. *(if the gnudi are too soft, add 1/4 cup more semolina flour and re-scoop)
Rest the gnudi in the fridge, uncovered for a minimum of 1 hour.
When ready to cook, make the sauce. In a sauté pan over low heat, melt the butter. Once melted, add the lemon juice and a pinch of salt. The herbs will be added after the gnudi are cooked.
Bring a large pot of salted water to a bare simmer. Working with a few gnudi at a time, gently place them into the pot and cook for about 3–4 minutes. Gently remove them with a slotted spoon and place them in the butter sauce.
Once all the gnudi are cooked, add the herbs and cook the butter sauce on low-medium for 1-2 minutes, finishing the gnudi off. Serve immediately.